Further characterization of carbonaceous materials in Hayabusa‐returned samples to understand their origin     

Masayuki Uesugi  Motoo Ito  Hikaru Yabuta  Hiroshi Naraoka  Fumio Kitajima  Yoshinori Takano  Hajime Mita  Yoko Kebukawa  Aiko Nakato  Yuzuru Karouji 《Meteoritics & planetary science》2019,54(3):638-666

Carbonaceous materials in the sample catcher of the Hayabusa spacecraft were assigned as category 3 particles. We investigated the category 3 particles with a suite of in situ microanalytical methods. Possible contaminants collected from the cleanrooms of the spacecraft assembly and extraterrestrial sample curation center (ESCuC) were also analyzed in the same manner as category 3 particles for comparison. Our data were integrated with those of the preliminary examination team for category 3 particles. Possible origins for the category 3 particles include contamination before and after the operation of the Hayabusa spacecraft.  相似文献   

Soil column experiments for iodate and iodide using K-edge XANES and HPLC–ICP-MS     

Yoko S. Shimamoto  Takaaki Itai  Yoshio Takahashi 《Journal of Geochemical Exploration》2010

Radioactive iodine is one of the most problematic radionuclides because of its long half life and high mobility. Mobility of iodine depends on the chemical form to a great extent. This paper reports the results of soil column experiments we conducted to evaluate the mobilities of IO₃⁻ and I⁻. In order to determine the mechanisms of adsorption of IO₃⁻ and I⁻ on soil, adsorption isotherms were obtained by batch experiments. Both adsorption isotherms of IO₃⁻ and I⁻ are well explained by Langmuir model. The adsorption maximum of IO₃⁻ is about five times larger than that of I⁻. In the column experiments, iodine distributions between soil and pore water in the soil column were determined at various depths. Chemical forms of iodine in soil and pore water were determined by X-ray absorption near-edge structure (XANES), and high performance liquid chromatography connected to inductively coupled plasma mass spectrometry (HPLC–ICP-MS), respectively. Vertical profiles of iodine in pore water were simulated using Visual MODFLOW. Our results showed, upon I⁻ infiltration through the column, that a small amount of I⁻ adsorbed on soil, and its mobility is mainly controlled by advection and dispersion. The profile of iodine concentration in pore water was well simulated by assuming equilibrium-controlled Langmuir type adsorption without considering any chemical transformations. For the IO₃⁻ addition system into the column, however, IO₃⁻ adsorbed to soil to a larger degree, which causes a much larger retardation effect than I⁻. In addition, reduction of IO₃⁻ to I⁻ was also confirmed in both soil and pore water by XANES and HPLC–ICP-MS, respectively. The fraction of I⁻ increased toward the deeper end in both phases because of its lower affinity for soil than IO₃⁻, where the reduced I⁻ was released to the pore water and transported by the water flow. In this study, such reduction effect was clearly demonstrated by the speciation analyses of iodine in both soil and water phases, which confirmed that the mobility of I⁻ is a dominant factor that controls the fate of iodine in the surface environment.  相似文献   

Alteration of ferrihydrite reductive dissolution and transformation by adsorbed As and structural Al: Implications for As retention     

Yoko Masue-Slowey  Scott Fendorf 《Geochimica et cosmochimica acta》2011,75(3):870-508

Reduction of As(V) and reductive dissolution and transformation of Fe (hydr)oxides are two dominant processes controlling As retention in soils and sediments. When developed within soils and sediments, Fe (hydr)oxides typically contain various impurities—Al being one of the most prominent—but little is known about how structural Al within Fe (hydr)oxides alters its biotransformation and subsequent As retention. Using a combination of batch and advective flow column studies with Fe(II) and Shewanella sp. ANA-3, we examined (1) the extent to which structural Al influences reductive dissolution and transformations of ferrihydrite, a highly reactive Fe hydroxide, and (2) the impact of adsorbed As on dissolution and transformation of (Al-substituted) ferrihydrite and subsequent As retention. Structural Al diminishes the extent of ferrihydrite reductive transformation; nearly three-orders of magnitude greater concentration of Fe(II) is required to induce Al-ferrihydrite transformation compared to pure two-line ferrihydrite. Structural Al decreases Fe(II) retention/incorporation on/into ferrihydrite and impedes Fe(II)-catalyzed transformation of ferrihydrite. Moreover, owing to cessation of Fe(II)-induced transformation to secondary products, Al-ferrihydrite dissolves (incongruently) to a greater extent compared to pure ferrihydrite during reaction with Shewanella sp. ANA-3. Additionally, adsorption of As(V) to Al-ferrihydrite completely arrests Fe(II)-catalyzed transformation of ferrihydrite, and it diminishes the difference in the rate and extent of ferrihydrite and Al-ferrihydrite reduction by Shewanella sp. ANA-3. Our study further shows that reductive dissolution of Al-ferrihydrite results in enrichment of Al sites, and As(V) reduction accelerates As release due to the low affinity of As(III) on these non-ferric sites.  相似文献   

Compositional diversity in insoluble organic matter in type 1, 2 and 3 chondrites as detected by infrared spectroscopy     

Yoko Kebukawa  Conel M.O’D. Alexander 《Geochimica et cosmochimica acta》2011,75(12):3530-3541

Insoluble organic matter (IOM) isolated from 22 carbonaceous and ordinary chondrites spanning a wide range of groups and petrologic types were analyzed using Fourier transform infrared spectroscopy (FTIR). Based on common IR spectral features, it is observed that IOM falls into 4 molecularly distinct groups (designated here as A through D). Spectral group A includes type 1 and 2 chondrites and exhibits intense aliphatic C-H and carboxyl vibrational peaks. Spectral group B includes the least metamorphosed type 3 chondrites and Tagish Lake, and exhibits weaker aliphatic and carboxyl vibrational intensity. Spectral groups C and D include metamorphosed type ?3.1 chondrites and a heated CM chondrite. The carbonyl stretching features in spectral groups C and D differ from that in spectral groups A and B and from each other. In spectral group C, the carbonyl stretching is assigned to cyclic unsaturated lactones; in spectral group D carbonyl exists predominantly in the form of unsaturated ketone moieties. Both spectral groups C and D have a relatively narrow band structure around 1210 cm⁻¹ (assigned to aromatic skeletal modes) as compared with spectral groups A and B, which is consistent with the formation of more condensed aromatics by extensive thermal metamorphism. The differences in carbonyl structures in spectral groups C and D are not the result of different effective metamorphic temperatures, rather these differences likely result from variation in the activity of water and oxygen at different stages of parent body metamorphism. Such environmental variations must be local phenomena in the parent bodies as there is no correlation between spectral grouping and chondrite class or group.  相似文献   

Importance of instantaneous radiative forcing for rapid tropospheric adjustment     

Tomoo Ogura  Mark J. Webb  Masahiro Watanabe  F. Hugo Lambert  Yoko Tsushima  Miho Sekiguchi 《Climate Dynamics》2014,43(5-6):1409-1421

To better understand CFMIP/CMIP inter-model differences in rapid low cloud responses to CO₂ increases and their associated effective radiative forcings, we examined the tropospheric adjustment of the lower tropospheric stability (LTS) in three general circulation models (GCMs): HadGEM2-A, MIROC3.2 medres, and MIROC5. MIROC3.2 medres showed a reduction in LTS over the sub-tropical ocean, in contrast to the other two models. This reduction was consistent with a temperature decrease in the mid-troposphere. The temperature decrease was mainly driven by instantaneous radiative forcing (RF) caused by an increase in CO₂. Reductions in radiative and latent heating, due to clouds, and in adiabatic and advective heating, also contribute to the temperature decrease. The instantaneous RF in the mid-troposphere in MIROC3.2 medres is inconsistent with the results of line-by-line (LBL) calculations, and thus it is considered questionable. These results illustrate the importance of evaluating the vertical profile of instantaneous RF with LBL calculations; improved future model performance in this regard should help to increase our confidence in the tropospheric adjustment in GCMs.  相似文献   

Comparison of FT‐IR spectra of bulk and acid insoluble organic matter in chondritic meteorites: An implication for missing carbon during demineralization     

Yoko Kebukawa  Conel M. O'D. Alexander  George D. Cody 《Meteoritics & planetary science》2019,54(7):1632-1641

Past studies of the various separable carbonaceous fractions have been unable to account for all of C in primitive chondrites. In particular, up to 20–50% of the C is lost during acid leaching of bulk samples even after the C in carbonates and soluble organic matter is accounted for. To try to better characterize the nature of this “missing C,” we have compared the bulk infrared (IR) absorption spectra of a number of primitive chondrites with those of their previously reported insoluble organic matter (IOM). The aliphatic C–H stretching bands, in particular, allow us to compare the molecular structures of bulk C with that of IOM. The spectral differences between bulk C and IOM reflect “missing C” phases that were lost during acid leaching, although we cannot completely exclude the possibility that the OM was modified after demineralization. Comparing IR spectra of bulk meteorite powder and IOM suggests that the missing C varies in its molecular structure, and that mildly thermally metamorphosed type 3 chondrites tend to be richer in an aliphatic fraction with lower CH₂/CH₃ ratios, relative to IOM, compared to aqueously altered carbonaceous chondrites (CI/CM/CR). The missing C is most likely released from acid‐labile functional groups, such as esters, acetals, and amides, during demineralization, although it cannot be ruled out that some fraction of the missing C is in small grains that are difficult to recover from suspension, or in water‐soluble compounds trapped in phyllosilicates.  相似文献   

Human impacts on large benthic foraminifers near a densely populated area of Majuro Atoll, Marshall Islands     

Yoko Osawa  Yu Umezawa  Yoichi Ide  Toshihiro Miyajima 《Marine pollution bulletin》2010,60(8):1279-1287

Human impacts on sand-producing, large benthic foraminifers were investigated on ocean reef flats at the northeast Majuro Atoll, Marshall Islands, along a human population gradient. The densities of dominant foraminifers Calcarina and Amphistegina declined with distance from densely populated islands. Macrophyte composition on ocean reef flats differed between locations near sparsely or densely populated islands. Nutrient concentrations in reef-flat seawater and groundwater were high near or on densely populated islands. δ¹⁵N values in macroalgal tissues indicated that macroalgae in nearshore lagoons assimilate wastewater-derived nitrogen, whereas those on nearshore ocean reef flats assimilate nitrogen from other sources. These results suggest that increases in the human population result in high nutrient loading in groundwater and possibly into nearshore waters. High nutrient inputs into ambient seawater may have both direct and indirect negative effects on sand-producing foraminifers through habitat changes and/or the collapse of algal symbiosis.  相似文献   

Flocculation and particle size analysis of expansive clay sediments affected by biological, chemical, and hydrodynamic factors     

Xiaoling Tan  Liming Hu  Allen H. Reed  Yoko Furukawa  Guoping Zhang 《Ocean Dynamics》2014,64(1):143-157

Expansive clay sediments are abundant in riverine and estuarine waters and bottom beds, and their particle size distributions (PSD) are important for the analysis of sediment transport. This paper presents an experimental study to evaluate, using a laser particle size analyzer under varying flow conditions, the intrinsic PSD of two expansive clays, a Ca- and a Na-montmorillonite and the influence of biological, chemical, and hydrodynamic factors on their flocculation and PSD. The considered biological factor consists of three extracellular polymeric substances of varying polarity, including xanthan gum, guar gum, and chitosan; the chemical factor is the salinity; and the hydrodynamic factor is the types of flow indicated by the Reynolds number and shear rate. The intrinsic PSD of both clays show a multimodal lognormal distribution with sizes ranging from 0.2 to 50 μm. All three biopolymers, xanthan gum, guar gum, and chitosan, can facilitate flocculation through long-range polymer bridging and short-range ion-dipole interaction, hydrogen bonding, and Coulomb force. The influence of salinity is different for the two clays: the particle size of the Na-montmorillonite increases with salinity, which is caused by flocculation resulting from the suppressed electrical double layer, while that of the Ca-montmorillonite is slightly reduced owing to the decreased basal spacing and cation exchange. For different hydrodynamic conditions, higher shear rate promotes the flocculation of Ca-montmorillonite, but breaks the Na-montmorillonite flocs. The significance of understanding the flocculation and PSD of expansive clays is also discussed in terms of sediment transport under different aquatic environments.  相似文献   

Dietary analysis of harbour seals (Phoca vitulina) from faecal samples and overlap with fisheries in Erimo,Japan          下载免费PDF全文

Tabitha C. Y. Hui  Yuka Morita  Yumi Kobayashi  Yoko Mitani  Kazushi Miyashita 《Marine Ecology》2017,38(3)

The number of harbour seals in Japan has been rebounding since protection began in the mid‐1980s. With the increase in seal numbers, increased conflict with fisheries has occurred through depredation and the belief that seals compete with fisheries for prey. However, competition can only be determined if the prey species and quantities seals consume over time are known. We studied the diet of harbour seals in Erimo, site of the largest population of harbour seals in Japan, from 2011 to 2012 and assessed the degree of prey overlap with local fisheries. We used both hard parts and DNA techniques to identify prey items in seal scats, and compared these results to local fisheries data. A total of 46 prey occurrences was detected by both methods, of which 17 matched between techniques at least to the family level. Hard parts methods identified five incidences of prey undetected by DNA methods in five scats (one incidence per scat). DNA methods identified 24 additional prey occurrences in 13 scats, for which no hard part evidence for that prey had been found. This more than doubled the total number of prey occurrences across the 15 scats compared. Overall, the most frequently occurring harbour seal prey were walleye pollock (Theragra chalcogramma), sculpins and snailfishes. In contrast, the top three groups targeted by fisheries were codfishes, salmon and invertebrates. Many species common in the harbour seal's diet such as snailfishes and blennies were not targeted by fisheries. Fishes such as greenlings, sculpins, rockfishes and Japanese anchovy (Engraulis japonicus) were common in the diet of harbour seals, but made up a very small proportion of fisheries catches in Erimo. The importance of other prey species varied between seasons. Sculpins, greenlings and forage fishes were the top three prey groups for harbour seals in spring by percent modified frequency of occurrence, whereas the most important target groups by percentage mass caught by fisheries were codfishes, cephalopods and other invertebrates. Sculpins and rockfishes remained as important prey items for harbour seals in summer and autumn, in addition to codfishes, snailfishes and blennies. In contrast, the main groups caught by fisheries in summer were other fishes, particularly Japanese amberjack (Seriola quinqueradiata) and various species of sharks and eels, and invertebrates. By autumn, Erimo fisheries had focussed on catching salmon. Salmon were taken by harbour seals as well during this period, but at a relatively lower frequency compared to other prey groups. The results of our study show that although harbour seals consumed several of the prey species targeted by fisheries, the relative importance of these species to seals and fisheries and the seasons in which they were targeted were different.  相似文献   

Individual exposure to particulate matter in urban and rural Chinese households: estimation of exposure concentrations in indoor and outdoor environments     

Guo  Minna  Xing  Rui  Shimada  Yoko  Kurata  Gakuji 《Natural Hazards》2019,99(3):1397-1414

Natural Hazards - According to the World Health Report, an estimated 540,000 people in China died prematurely due to indoor air pollution in 2009. The major source of indoor air pollution is the...  相似文献